1. Field of the Invention
This invention relates to a high-frequency dielectric material suitable for a high-frequency resonator, a resonator, and methods for producing the same.
2. Background Art
As substrate materials for use in electrical and electronic printed circuit boards, there have been developed some which can be sintered at low temperature. Using these, it is possible to sinter the substrate material, conductors, resistors and the like, simultaneously and integrally, at a low temperature of or below 1,000.degree. C., for example. Such low-temperature sintered boards are used at frequencies in the low-frequency band of, for example, about 0.5 GHz or lower, and as the substrate material there is generally used a low sintering temperature material containing glass having a softening point of about 700.degree.-900.degree. C. and Al.sub.2 O.sub.3 aggregate.
The inventors test-fabricated a high-frequency resonator by laminating dielectric layers formed using the low sintering temperature material mentioned above and forming a strip line between these dielectric layers to obtain a tri-plate circuit.
However, the dielectric constant of the dielectric layers formed using the low sintering temperature material varied with temperature. For example, the dielectric constant temperature coefficient .tau..epsilon. at a frequency of 2 GHz was about 130 ppm/.degree.C. It was thus found that when the resonator is used in a high-frequency band, for example at a frequency of 0.5 GHz or higher, its resonant frequency varies greatly with temperature, making it difficult to use in practical applications.